The article considers a discrete model of a typical airframe component for determining the interface surfaces of various elements of a unit (a component) structure during technological preparation of assembly production. An algorithm for determining the reference points of all surfaces for locating a product in the assembly position based on its electronic model is proposed. The data obtained make it possible to consider the part as a whole and to determine the nature of its relationships with other parts that are included in the assembly unit. That is, to determine the conjugation surfaces and choose limiting constraints using production rules. Thus, if for different parts, two surfaces formed by a set of points have a minimum of three points with the same coordinates, the parts are considered to be mateable, and the surfaces are conjugated surfaces. The algorithm for determining the maximum distances between the reference points allows, as a result, determining the minimum number of locators of the assembly tooling. When determining the composition of assembly bases, the mathematical apparatus of the set theory, vector algebra, mathematical logic, and elements of the pattern recognition theory are applied. The source of the data for it is the electronic model of the product, made in the CAD system of Siemens NX. The acquisition of data from the electronic product model is carried out with the help of the CAD system software and the associated product data management integrated environment. This frees the technologist from performing routine operations and reduces the likelihood of subjective factors impact.